Internal combustion engine with a turbo-compressor



Aug. 20, 1968 c. HUBERS 3,397,532

INTERNAL COMBUSTION ENGINE WITH A TURBO-COMPRESSOR Filed Jan. 10, 1966 FlG.1

FIG.2

INVENTOR. 60W e /#'.5 Hub 812s 0710A NIYS 3,397,532 INTERNAL COMBUSTION ENGINE WITH A TURBO-COMPRESSOR Cornelis Hubers, 30 Molenweg, Rozenburg, Netherlands Filed Jan. 10, 1966, Ser. No. 519,643 3 Claims. (Cl. 60-13) ABSTRACT OF THE DISCLOSURE An internal combustion engine provided with a turbocompressor driven by exhaust gases and delivering pressurized air on the order of the maximum combustion pressure of the engine to the cylinders thereof. The pressurized air serves as an extra air source for the engine cylinders and is supplied during the first part of the working stroke of the pistons, the fuel being supplied after the main part of the extra air has been supplied to the chamber. This combination allows the engine power to be increased to such an extent that a maximum combustion pressure is obtained which is comparatively low relative to the average piston pressure, the latter being as high as twice what has been realized in the prior art, thereby resulting in a lighter engine construction achieving the same engine power.

This invention relates to internal combustion engines.

An internal combustion engine comprising at least one working cylinder and an air compressor, said air compressor being adapted to compress air to a pressure equal to or slightly less than the maximum combustion pressure occurring in each working cylinder, said air being supplied to said working cylinder or cylinders as an additional air quantity relative to the air compressed in said working cylinder or cylinders such that an extra large degree of filling is brought about is known from the German patent specification 525,527. According to said patent specification the additional air is compressed in a compressor driven by the engine shaft and is supplied, mixed with oil vapour and preheated or not preheated, to the working cylinder after a combustion of fuel has taken place therein, said fuel having been injected at the beginning of the working stroke. In this way a larger degree of filling of the cylinder and consequently a larger engine power are obtained. However, at a normal stroke/diameter ratio of the working cylinder, as a result of the larger degree of filling of the cylinder, a considerable amount of pressure energy is lost in the exhaust gases. Moreover, because the injection of fuel is effected at the beginning of the working stroke, the maximum combustion pressure in the cylinder will be high.

The invention aims at increasing the engine power per cylinder by the application of a larger degree of filling of the cylinder without the above-mentioned high loss of pressure of the expansion gases and with a maximum combustion pressure which is comparatively low relative to the average piston pressure. In the engine according to the invention the average piston pressure may be twice as high as realized so far in practice.

This is accomplished according to the invention by providing an internal combustion enginecomprising at least one working cylinder and an air compressor, said air compressor being adapted to compress air to a pressure equal to or slightly less than the maximum combustion pressure occurring in each working cylinder, said air being supplied to said working cylinder or cylinders as an additional air quantity relative to the air compressed in said working cylinder or cylinders such that an extra large degree of filling is brought about, the additional air being supplied during the first part of the working stroke and fuel being supplied during or at the end of the additional supply of air, the high pressure of the exhaust Q United States Patent 3,397,532 Patented Aug. 20, 1968 ice gases occurring as a result thereof being utilized in a turbine driven by said exhaust gases said turbine driving the air compressor.

It is to be noted that the application of an exhaust gas turbine driving an air compressor in an engine is generally known per se. However, this always applies to after-supercharging, as for example according to the German patent specification, or pre-supercharging. In the latter case the scavenging air of the engine is supplied as air compressed by the turbo-compressor to a pressure exceeding the atmospheric pressure. In neither of these two cases the average piston pressure is as high as according to the invention.

It is furthermore to be noted that in the US. Patent 2,477,230 an internal combustion engine is described in which compressed air is supplied in the working cylinder at the beginning of the working stroke. However, the fuel is injected before the end of the compression stroke so that consequently the combustion pressure in the cylinder has already been considerably increased at the end of the compression stroke. The subsequently supplied compressed air must have a pressure which is higher than the maximum combustion pressure, and on account of the fact that this air, like the fuel, is supplied approximately at the dead center position of the piston the cylinder pressure still more increases.

In consequence of the fact that according to the invention as a result of intermediate supercharging an additional quantity of air is supplied the degree of filling is large at a comparatively low pressure.

Since in the engine according to the invention the combustion gases are expelled from the cylinder at a high pressure and high temperature, said high temperature at a high engine load may be noxious to the vanes of the exhaust gas turbine.

A preferred embodiment of the engine according to the invention is therefore provided with a by-pass conduit between the compressor exhaust and the inlet of the exhaust gas turbine, there being included in said by-pass conduit a regulable valve adapted to be regulated depended on the temperature of the exhaust gases at the turbine inlet.

The invention will be further explained below with reference to the accompanying drawings showing by way of example two embodiments of a two-stroke engine according to the invention.

FIG. 1 shows diagrammatically a first embodiment of such an engine.

FIG. 2 is a diagram of a second embodiment with a receiver for the exhaust gases.

The engine shown in FIG. 1 comprises a number of cylinders 1 of which the exhaust ports are connected to a common exhaust conduit 2 leading to a turbine 3 adapted to be driven by the exhaust gases. Said turbine is coupled with a multi-stage air compressor 4 of which an outlet branch pipe at the end of the first stage is connected via a conduit 5 to an air chamber 6. This air chamber 6 serves as a scavenging air reservoir and is connected via conduits 7 to the scavenging ports of the variou cylinders 1. An exhaust branch pipe at the end of the last stage of the compressor 4 is connected via a conduit 8 to a reservoir 9 for the intermediate supercharging air. From said reservoir 9 a conduit 10 leads with branches to the various cylinders. In each cylinder head a controlled inlet valve 11 is provided in a connecting channel between the end of the branch to the conduit 10 and the cylinder space.

The engine according to FIG. 1 operates as follows:

When the engine is started with the aid of the starting air reservoir, the fuel supply is switched on after which the fuel ignites and the engine continues to operate under its own power. The exhaust gases drive the turbine 3 and the latter in turn drives the compressor 4. This compressor supplies the scavenging air for the cylinders so that at the downward piston stroke, when the piston opens the scavenging ports, said scavenging air flows from the reservoir 6 into the cylinder and the gases are discharged to the conduit 2. At the return piston stroke first the exhaust ports and thereafter the scavenging ports in the cylinder are closed after which a remainder of scavenging air is compressed. At the beginning of the downward piston stroke or shortly thereafter the inlet valve 11 is opened and consequently highly compressed air, originating from reservoir 9 with intermediate supercharging air, enters the cylinder. After the valve 11 is closed again the supply of fuel from fuel supply means 16 and the ignition by ignition means 17 respectively take place. In consequence of the fact that in the meantime the piston is moving downwards already at a rather high velocity, the pressure in the cylinder increases only slightly above the pressure which prevails in the cylinder after the admission of the intermediate supercharging air. Consequently a high degree of filling of the cylinder is obtained and therefore a high average piston pressure without the occurrence of a high maximum combustion pressure.

In order to prevent the vanes of the turbine 3 from being damaged by a too high temperature of the exhaust gases a by-pass conduit 12 is provided between the compressor exhaust and the turbine inlet. In this conduit 12 a valve 13 i included which is controlled dependent on the temperature of the gases at the turbine inlet and which opens at a too high temperature of these gases so that a quantity of compressed air flows to the turbine inlet and mixes with the hot gases so that these are cooled.

In the second embodiment of the engine according to the invention, shown in FIG. 2, in order to render the pressure of the exhaust gases in the conduit 2 more uniform there is provided between said conduit and the various cylinder exhaust openings a common receiver 14. The advantage of such an arrangement is that for the exhaust gas turbine 3 an action turbine may be utilized. Furthermore in this embodiment the more preferable uniflow scavenging of the cylinders is applied in contrast with the reverse scavenging as applied according to FIG. 1. For this purpose a controlled exhaust valve 15 is provided in each cylinder head. With this valve it is also possible to have the engine operate without compression and to have the entire filling effected by means of the valve 11.

It is obvious that the invention is not restricted to the embodiments described above and shown in the drawings but that various modifications may be made within the scope of the invention.

For instance instead of exhaust and scavenging ports, valves may be applied. This is particularly to be preferred if instead of the pulse system for the supply to the supercharger a constant pressure system is used by interposition of a buffer reservoir. It is thereby advisable, in view of the high nominal value of the buffer pressure, to close the exhaust valve only when (apart from the possibility of presupercharging) the piston has reached the position in which the same pressure would have been obtained without any supercharging.

The exhaust gas turbine with turbo-compressor may be replaced by a rotary piston-compressor adapted to be coupled to the engine shaft which when maneuvering ensures a more accurate operation.

I claim:

1. An internal combustion engine comprising at least one working cylinder, means to supply air thereto, a piston movable in said cylinder to compress said air therein, an air compressor designed to deliver air under a pressure equal to the maximum combustion pressure occurring in said working cylinder, means for supplying the air compressed by said compressor to said working cylinder in addition to the air compressed in said working cylinder whereby an extra large degree of filling of said cylinder is brought about, first control means for controlling said additional air supplying means to supply the additional air during the first part of the engine piston working stroke, means for injecting fuel into said cylinders, second control means for controlling said fuel injecting means to supply fuel substantially only at the end of the supply of the additional air for combustion therewith, a turbine driven by exhaust gases from said engine, said exhaust gases having a high pressure as a result of the operation of the above-mentioned means, said turbine being operatively connected to drive said air compressor.

2. An internal combustion engine according to claim 1 further comprising a by-pass conduit operatively connected between a compressor exhaust port and an inlet to the exhaust gas turbine, a regulatable valve in said by-pass conduit adopted to be regulated dependent upon the temperature of the exhaust gases at the turbine inlet whereby air from said compressor is allowed to selectively mix with and thereby cool the exhaust gases.

3. An internal combustion engine comprising at least one working cylinder having a piston movably mounted therein to compress air in said working cylinder, said cylinder including an inlet, a scavenging port, and an exhaust port, a turbine operatively connected to said exhaust port, a compressor connected to and driven by said turbine, an output of said compressor being operatively connected to said scavenging port, said air compressor delivering air at a pressure no greater than the maximum combustion pressure occurring in said Working cylinder, means for supplying the air compressed by said compressor to said working cylinder through said inlet in addition to the air compressed therein whereby said cylinder is filled to an extra large degree, first control means for controlling said means for supplying additional air to supply said air during the first part of the engine piston working stroke, fuel injecting means for each cylinder, second control means for controlling said fuel injecting means for supplying fuel substantially only at the end of the supply of the additional air for combustion therewith.

References Cited UNITED STATES PATENTS 548,142 10/1895 Schumrn 123-26 2,010,469 8/1935 Triebnigg 12326 2,189,106 2/ 1940 Garve 6013 2,477,230 7/1949 Bell 123-26 2,995,890 8/1961 Dolza 12326 3,113,561 12/ 1963 Heintz 123-65 FOREIGN PATENTS 421,110 12/ 1934 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner.

D. HART, Assistant Examiner. 

